Fibrous structures with fine particles

ABSTRACT

A fibrous structure comprising a fibrous matrix with surrogate particles fixed to the fibrous matrix, is provided. Functionally active, fine particles are immobilized on the fixed surrogate particles.

FIELD OF THE INVENTION

This invention relates to a fibrous structure with immobilizedparticles.

BACKGROUND OF THE INVENTION

Carrier particles for sorptive impregnants are known. Exemplary areconventional sorptive impregnants such as copper and silver salts, onactivated carbon particles.

Fibrous structures containing functionally active particles arecommercially available. Filter media or filters made from thesestructures include sorptive particles for selectively removing certaincomponents of a liquid or gas passing through the filter. Acceptableperformance with low pressure drop beneficially results from the activeparticles being distributed in a three dimensionally spaced apartarrangement. Advantageously, the supporting fibrous structure isstabilized by fiber-fiber bonding, and the active particles are bondedto, or entrapped in interstitial spaces of, the fibrous structure.

Fine active particles will beneficially provide more surface area for adesired end use than a comparable volume of larger particles, but theremust be accessibility to the fine particles by a gas or liquid beingpassed through the fibrous structure. Difficulties exist when activeparticles are fine, in particular submicron in size. For example,control of the movement of fine particles when introducing fineparticles into or onto a fibrous structure, is challenging because ofthe mobility or irregular motion of fine particles. Fine, mobileparticles also tend to cover available fibrous surface area, and thusmay interfere with subsequent fiber-fiber bonding.

Immobilization of fine, mobile particles to prevent loss during use ishighly desirable. The immobilization requires adequate surface area fordeposition of the fine particles. However, an equivalent volume of fineparticles requires more surface area for deposition than would berequired by an equivalent volume of conventionally-sized particles, forinstance, having an average diameter in the range of approximately 300to 500 microns. Enough fiber surface will typically not be available ina fibrous structure of macrofibers, for surface bonding of a usefulloading of fine active particles. Additionally, the need for the fibrousstructure to have an acceptably low pressure drop will typicallyconflict with enough fiber surface. Moreover, even if excess fibersurface were available, the immobilization must be efficient so thatloss during use will be minimized.

Accordingly, an improved fibrous structure having a three dimensionalarrangement of immobilized active material, is needed. Such a fibrousstructure would benefit the use, and provide increased surface for theimmobilization, of fine, mobile particles as the active material, butnevertheless have acceptably low pressure drop. Such a fibrous structurewould advantageously provide accessibility of fine active particles to agas or liquid being passed through the fibrous structure, yet minimizethe loss of fine active particles during use.

SUMMARY OF THE INVENTION

In accordance with the present invention, an improved fibrous structureis beneficially based upon a fibrous matrix and surrogate particlessupported by the fibrous matrix. By "surrogate particles" is meantparticles that function as a carrier for functionally active particles.

In accordance with the invention, the surrogate particles arebeneficially distributed and fixed in a three dimensional arrangement.By the term "fixed" is meant bonded to, or entrapped in interstitialspaces of, the fibrous matrix. Advantageously, the fibrous matrix isgenerally uniform in structure, and the three dimensional arrangement isalso generally uniform.

In accordance with the invention, active particles of fine size arecarried by considerably larger, surrogate particles, and there isselective deposition of fine, mobile active particles on fixed surrogateparticles. The selective deposition is beneficially based upon apreferential attraction between the fine, mobile particles and the fixedsurrogate particles. The methodology selected for the depositionadvantageously provides for immobilization of the fine active particleson the surrogate particles.

Adequate surface area for the deposition, and accessibility to theimmobilized fine particles by a liquid or gas, are benefitted byappropriate choice of the surrogate particles taking into consideration,for instance, the average size of the fine particles and physicalstructure of the surrogate particles. Also beneficially influencing theaccessibility are deposition of the fine particles as a monolayer on theindividual surrogate particles, and generally uniform, three dimensionalspacing of the surrogate particles; accordingly, these features arepreferred.

In a related embodiment, functionally active, fine particles areimmobilized on high available surface, surrogate particles fixed in athree dimensional arrangement. In accordance with the present invention,the immobilized fine particles will typically provide the fibrousstructure with a useful processing benefit, or analytical use, and/or afiltration function.

BRIEF DESCRIPTION OF THE DRAWING

Reference is now made to the accompanying drawing, which is highlyillustrative, and forms a part of the specification of the presentinvention.

FIG. 1 is a sectional view depicting a fibrous structure containingsurrogate particles, in accordance with the invention; and

FIG. 2 is an enlarged view of a surrogate particle bearing immobilizedfine active particles, and entrapped within an interstitial space of,and bonded to, fibers of the fibrous structure of FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

As indicated above, the fibrous structure of the present invention isadvantageously based upon a synthetic fibrous matrix with surrogateparticles distributed and fixed in a three dimensional arrangement. Sucha structure will be typically non-woven, and may be made using compositefibers, a mixture of structural fibers and fusible fibers, powderbonding, or using other suitable approaches for bonding the surrogateparticles to the fibrous structure. The surrogate particles may also befixed by physical techniques such as needling and water jet entangling,which result in entrapment.

In any event, the fibrous matrix will include a structural fibrouscomponent, and beneficially the structural component will providestructural integrity even when the fibrous matrix is highly loaded withthe surrogate particles. If heat is used for fixing the surrogateparticles, heat in the form of radiant heat such as IR heat, may beadvantageously selected so that bonding is effected without compressionor pressure-induced distortion of the surrogate particles/fibrous matrixstructure; and the bonding temperature will typically be an elevatedtemperature in the range of from about 130 to 200° C., although anelevated temperature outside this range may be appropriate dependingupon factors including the specific material for bonding the surrogateparticles to the fibrous matrix.

To provide for point-of-contact bonding of the surrogate particles tothe fibrous matrix, the fibrous matrix is preferably formed fromcomposite fibers having a structural fiber component and a heat-bondablefiber component. Generally speaking, the structural component willtypically melt at a temperature at least about 30 to 50° C. higher thanthe heat-bondable component. Preferably, the heat-bondable fibercomponent has high bonding capability for bonding the surrogateparticles to the fibrous matrix. The bonding is preferably achieved byheating a heat-bondable, polymeric fiber component to a temperature atwhich it is tacky or molten, but in any event provides for adhesion.Beneficially, the heating will also provide for stabilization of the webstructure by fiber-fiber bonding at the cross over points of fibers. A"spot weld" is produced by adhesion at the point of contact ofindividual surrogate particles with individual matrix fibers.Point-of-contact bonding advantageously minimizes undesirable coating ofthe surrogate particles by the bonding material, and hence unwantedreduction of the surface area of the surrogate particles available forattractive deposition and immobilization of fine, mobile activeparticles.

Concentric sheath-core fibers are one example of useful compositefibers. Suitable composite fibers also include eccentric sheath-corefibers, and fibers having a side-by-side configuration. Composite fibersof these types are known as bicomponent or heterofil fibers. One skilledin the art will recognize that a variety of multiconstituent fiberstructures having a lower melting component exist or may be made, andwill recognize that those multiconstituent fiber structures may beselected from, as useful composite fibers.

Useful fibers may be in a variety of forms including crimped andnon-crimped cut staple fibers, short-cut staple, continuous filaments,and blends thereof. Advantageously, a non-woven web structure inaccordance with the invention, may be dry-formed from crimped, staplefibers so as to be lofty. In addition, spunbond web structures and meltblown web structures may be used.

The structural fibers should be present in an amount sufficient toprovide a matrix structure and ample surface area for fixing thesurrogate particles. Typically, the fibrous matrix will be present in aminor amount compared to the loading of the surrogate particles.Although a fibrous web including surrogate particles may include fromabout 5% to 80% by weight of structural fiber, based on the combinedweight of the surrogate particles and the structural fiber, usually onlyabout 10 to 25 wt. % will be structural fiber unless low densitysurrogate particles are used.

The matrix structure will preferably be generally uniform to assist in apreferred, three dimensionally generally uniform distribution andspacing of the surrogate particles. In addition to promoting generallyuniform application and deposition of fine, mobile active particles onthe fixed surrogate particles, this characteristic benefitsaccessibility to the immobilized fine active particles by a liquid orgas. Tortuous flow paths may be provided by the three dimensionallyspaced apart arrangement of the surrogate particles. The use of acompressive force or other pressure to assist fixation of the surrogateparticles to the matrix structure, will work to the contrary and willtherefore be avoided.

An open, generally uniform, non-woven web structure in accordance withthe invention, may be beneficially dry-formed from crimped, staplemacrofiber having an average diameter in excess of about 10 microns. Theaverage diameter will typically range from about 12 to 25 micronsdepending upon the intended application. If desired, structural fibersof significantly different diameters may be combined to form the fibrousmatrix.

For dry lay processing, the structural fiber will generally have alength to diameter ratio that is limited on the low side. On the highside, continuous length fiber may be used. For wet lay processing, ifused, an appropriate length to diameter ratio of the structural fiberwill be selected.

Useful fibrous structures can be built to thicknesses of from about 0.5to 50 mm. However, if desirable, depending upon considerations includingthe end use, much thicker structures can be made. Stacked fibrousstructures can be made.

The fibrous matrix may also include a structurally beneficial amount ofstiffening fibers having a denier per filament of from 6 to 10,000especially if the surrogate particles are relatively large in size. Inaddition, the fibrous matrix may include microdenier fibers. Thesestiffening fibers or microdenier fibers may be composite ornon-composite fibers or a blend thereof. The fibrous matrix may includeother fibers or filament or fibrets, depending upon the result desired.

The surrogate particles may be any particles, organic or inorganic,suitable as a carrier for fine active particles. Especially usefulsurrogate particles will be porous and have rough or irregular surfacesproviding increased surface area for deposition. An advantageous voidvolume for surrogate particles is greater than about 50%, beneficiallyabout 60 to 65%, preferably greater than 70%, very preferably about 90%or more. The surrogate particles promote or will be modified to promoteselective deposition of fine, mobile particles on the surrogateparticles vis-a-vis the fibrous matrix. The surrogate particles may havea useful functional activity such as sorptive activity, for the end usedesired, but to be useful in this invention, that is not a requirementfor the surrogate particles. Thus, the surrogate particles may befunctionally inactive with respect to the desired end use. Suitablesurrogate particles include carbon particles such as activated carbon,zeolite particles, alumina particles such as activated alumina,polymeric particles including, for example, styrene monomer, andabsorbent particles such as commercially available superabsorbentparticles. The foregoing description is intended to be representative ofand not in limitation of particles suitable for use as surrogateparticles in the practice of the present invention.

Particularly suitable, surrogate particles are low density, porousparticles, and have pores and cavities including surface cavities,ranging in diameter from about 1 to 100 microns and interconnected bysmaller pores. These pores and cavities beneficially provide innersurface for deposition, in particular monolayer deposition, of fineparticles having an average size in the range of about 0.01 to 10microns, and thereafter for accessibility to the immobilized fineparticles. 1 cm3 of these surrogate particles provides in bulkapproximately 75 to 1,500 sq.m. of available surface. Polymericparticles of this type are available from Biopore Corporation. Bycomparison, 1 cm3 of a permeable non-woven web of 15 micron averagediameter fibers will provide only about 0.2 sq.m. of available surface.In accordance with the present invention, it is preferred thatfunctionally active, fine particles be deposited on a high availablesurface substrate, and in particular on high available surface,surrogate particles fixed in a permeable three dimensional arrangement.By the term "high available surface" is meant at least about 5,preferably at least about 25, sq.m. of available surface per cm3. Thisinvention is, of course, not limited to the use of high availablesurface, surrogate particles.

In accordance with the invention, the surrogate particles are bonded to,or entrapped within interstitial spaces of, the fibrous matrix, in abeneficially spaced apart, generally uniform, three dimensionalarrangement. Heat-bonding beneficially limits migration of the surrogateparticles within the structure, as well as loss from the structure.Bonding of individual surrogate particles to the fibrous matrix at morethan one point is advantageous. Heat-bonding may be achieved by, forinstance, the addition to the fibrous web of surrogate particles heatedto an appropriate elevated temperature, or by heating the web to anappropriate elevated temperature after the surrogate particles have beenadded to the web. The fixed surrogate particles may be only on the websurface, or within the web, or on the web surface and within the web.Heat-bonding without application of pressure to the surrogateparticles/fibrous matrix structure, beneficially avoids reduction ordistortion of the spacing between the surrogate particles.

The surrogate particles will typically have an average diameter in therange of from about 100 microns to about 1 mm to 10 mm, preferably about0.3 mm to 2 mm, may be in the form of beads, granules and so forth, andmay vary in shape from spheroidal beads to irregularly shaped particles.Generally speaking, the surrogate particles will have an appropriatesize to be entrapped by the web structure. However, the surrogateparticles may also be fixed by being preheated to an elevatedtemperature and then added to the web.

The fibrous matrix may be loaded with about 20% to 95% by weight of thesurrogate particles, based on the combined weight of the surrogateparticles and of the matrix fiber. In selecting the loading,consideration should be given to providing adequate surface area fordeposition of the selected amount of fine, mobile active particles onthe surrogate particles. A higher weight percent loading of one type ofsurrogate particle than another type of surrogate particle, will notnecessarily result in more surface area for deposition. For instance, ahigh loading of low density surrogate particles could result in highavailable surface for deposition, yet constitute only a low weightpercent, for instance, 25 wt. %. If surrogate particles similar indensity to activated carbon or zeolite or alumina are chosen, thefibrous matrix will typically be loaded with about 50% to 90% by weightof the surrogate particles, depending, of course, upon in particular thesurface area required for deposition. Generally speaking, a relativelyhigher volume of the fibrous matrix occupied by the surrogate particles,will provide for tortuous flow paths in the fibrous matrix.

In accordance with the invention, fixed surrogate particles carryimmobilized, fine active particles. Although a variety of fine particleshaving a useful function may be used, beneficial fine particles willtypically function in a fibrous structure in accordance with theinvention, to produce a useful processing effect such as an alteration,change or chemical modification of a component or components of a liquidor gas in contact with the fine particles; a useful analysis; or auseful filtration or separation function. Useful processing effectsinclude killing or inactivating or attenuating harmful bacteria andviruses, and chemically modifying undesirable inorganic contaminants.Useful diagnostic tests include those relating to DNA. The function ofthe fine active particles may be enhanced by functional activity of thesurrogate particles or by the functional activity of another substanceor material.

Fine active particles intended for use in the present invention, arecharacterized by mobility or irregular motion when suspended in a liquidor a gas, and thus will have an average size in the range of from about0.01 to 10 microns. Although submicron active particles are preferred,the present invention is applicable to fine particles up to 100 micronsin average size. In any event, the average size of the active particleswill be on the order of approximately 0.01 to 0.0001 of the average sizeof the surrogate particles. Therefore, a relatively larger average sizeof the active particles requires a larger average size of the surrogateparticles.

In accordance with the invention, the surrogate particles willadvantageously have pores or cavities, or pores and cavities largeenough for access to the inner surface of the surrogate particles anddeposition therein of fine active particles, and for accessibilitythereafter to the immobilized fine particles. Thus, the average poresize will be sufficiently larger than the average fine particle size sothat clogging of the pores by the fine particles is minimized and thegas or liquid can contact the immobilized fine particles. In additionfor accessibility, it will be beneficial for the fine particles to bedeposited in a monolayer. Accordingly, it is highly preferred that theavailable surface for deposition be at least approximately equal to, orbe slightly in excess of, the surface needed for monolayer deposition.Therefore, the relative average size of the fine active particles issignificant as to whether or not particular surrogate particles willprovide adequate surface area for deposition, in particular monolayerdeposition, and accessibility thereafter to the immobilized fineparticles. As will be understood, the deposition will take advantage ofthe entire available surface, that is, both inner and outer surface, ofthe surrogate particles.

Exemplary functionally useful organic and inorganic compounds in theform of fine particles, include materials useful for processing,analysis, filtration and separation. Processing effects include publichealth and medical applications using fine particles as modifiers ofinorganic contaminants, and biocidal fine particles, and includechemical applications using chemically reactive fine particles, andcatalysis by catalytic fine particles, and so forth. Exemplary fineparticulate, processing materials include silicates, synthetic amorphoussilica and alumina. Analytically useful fine active particles formedical, veterinary and other diagnoses, may be used. Alternatively orin addition, fine active particles such as activated carbon powder, mayprovide filtration. Fine active particles that perform a usefulseparation by removing one component from another component, may also beused. The fine active particles will be selected depending upon the enduse or function desired. The foregoing description is intended to berepresentative of and not in limitation of useful fine particles. Thefine active particles may be used alone, or in combination with anotherfunctionally active substance or substances. In addition to thesurrogate particles, the fibrous structure may include, to the extentconsistent with the need for selective deposition on the surrogateparticles, other particles significantly larger than the fine particles,and these optional large particles may be functionally active.

In accordance with the invention, a functionally effective amount offine active particles is post-fixation, immobilized on the fixedsurrogate particles. In this way, when the surrogate particles are fixedby bonding and also in the case of fiber-fiber bonding, bonding is notinterfered with by fine particles covering the bonding surface offibers. The loading of the fine particles will vary depending uponfactors including the intended function and the comparativeeffectiveness of the chemical or physical nature of the fine particlesfor the intended function. Accordingly, to obtain comparable functionalactivity, a relatively greater amount of relatively less effective, fineparticles will be used, whereas a relatively smaller amount ofrelatively more effective, fine particles will be appropriate. In anyevent, by the present invention, a functionally effective amount of thefine particles is immobilized, yet the fibrous structure will haveacceptably low pressure drop.

In accordance with the invention, fine, mobile active particles arebeneficially selectively deposited on fixed surrogate particles. By"selective" is meant significantly more, preferably substantiallyexclusive, deposition on the surrogate particles than on other availablesurface of the fibrous structure. To provide for selective deposition,the surrogate particles and the fine active particles will be chemicallyor physically, specifically attractive to one another; accordingly, whenthe surrogate particles are fixed by bonding to the fibrous matrix,point-of-contact bonding advantageously minimizes undesirable masking ofan attractive force, by the bonding material. A variety of methods andtechniques may be selected from, for the selective deposition, dependingupon factors including the basis for the selective deposition, thechemical and physical properties of the fine particles and the surrogateparticles, and the need to maintain the structural integrity of thefibrous matrix. Useful active deposition methodologies include chemicalor physical modification, grafting, plasma treatment, electrocharging,electrodeposition, chemical bonding and other suitable techniques. Ifheat is applied in a deposition methodology, the temperature selectedshould be less than that at which the desired product, including thefibrous matrix, is adversely affected. The deposition should be not onlyselective but also efficient so as to minimize loss, and to maximize theimmobilization, of fine, mobile active particles.

Depending upon the deposition methodology, the chemical and physicalproperties of the surrogate particles and the fine active particles, andother considerations, the fine active particles may be immobilized onand in the surrogate particles in various ways. The immobilization maybe by attractive association with, or being physically held orchemically bonded or otherwise attached to, the surrogate particles.Regardless, the immobilization must maintain accessibility to the fineactive particles, and must be efficient to minimize loss of the fineactive particles during use; and the manner of immobilization must beappropriate for the size of the fine particles. If chemically bonded,covalent chemical bonding could be an appropriate choice depending uponthe surface chemistry, for instance, bonding sites, of the surrogateparticles, and the size and chemistry of the fine particles. To effectimmobilization, the surrogate particles and/or fine particles may bechemically or physically modified to be specifically attractive to oneanother, for instance, to have attractive charges.

FIG. 1 shows at 20 a sectional view through a non-woven fibrousstructure in accordance with the invention. A plurality of individualfibers 22 form an open web 24, and define an upper surface 26 and alower surface 28 of the web. Beneficially, the fibrous matrix of the webis generally uniform and surrogate particles 30 are distributed in agenerally uniform, three dimensionally spaced apart arrangement withinthe web. Alternatively, the surrogate particles could be deposited onthe web surface only, or on the web surface and within the web.

The fibrous structure of FIG. 1 is advantageously dry formed fromcrimped staple macrofiber. Dry forming, and in particular carding,advantageously provides an open, generally uniform fibrous structure,and thereafter for controlled introduction and spacing of dissimilarmatter such as surrogate particles 30, with accessibility, yet tortuouspaths, in the surrogate particle-loaded structure for gas or fluid flow.

The surrogate particles are beneficially fixed so as to be maintained ina spaced apart relationship. Referring to FIG. 2, surrogate particlesare advantageously entrapped in interstices of the fibrous matrix andbonded to the fibrous matrix. Representative surrogate particle 30 hasan irregular surface with surface cavities 40 of varying sizes.Immobilized in cavities 40 are fine active particles, represented asdots or small circles disposed on the walls of and within the cavities.In addition, though not shown in FIG. 2 for reasons of simplifying thedrawing, fine active particles are also immobilized on the exteriorsurface of surrogate particles. Suitable surrogate particles will havepores and/or cavities large enough to accommodate the fine activeparticles to be deposited, and for accessibility of a gas or liquid tothe immobilized fine particles. It is undesirable for the relativeaverage size of the fine particles to be so close to the average poresize that the fine particles clog pores, because clogging will reducethe availability and efficacy of the immobilized fine active particlesto produce the intended functional result. In accordance with theinvention, there is selective deposition of the fine active particles onthe surrogate particles because of preferential attraction between thefine active particles and the surrogate particles, and the fine activeparticles are immobilized on fixed surrogate particles. Beneficially,the deposition on the available surface of the surrogate particles, isin a monolayer. In this way, a high loading of fine active particles isprovided in a relatively small volume with accessibility.

As also shown in FIG. 2, fibers 22 are advantageously sheath/corecomposite fibers each having a core 56 and a lower melting sheath 58.The surrogate particles are beneficially bonded to the fibers atnumerous points 66, the bonding being preferably localized, andfiber-to-fiber bonding at cross over points of the fibers stabilizes theweb structure. Because the bonding is effected prior to the depositionof the fine active particles, the bonding is not interfered with by fineparticles covering the bonding surface of the fibers. In addition, ifthe fine active particles were immobilized on the surrogate particlesand the surrogate particles thereafter deposited in the fibrousstructure, bonding of the surrogate particles to the fibrous structurewould detrimentally coat immobilized fine active particles, as well asblock and obstruct pores and cavities containing immobilized fine activeparticles, to a degree depending upon, for instance, the bondingtechnology used.

A fibrous structure in accordance with the invention, may have incontact therewith one or more other layers. These layers may benonwovens including partially densified nonwovens and melt blown webs,woven fabrics, knit fabrics, porous membranes and so forth. These layersmay be laminated to or otherwise suitably attached to the inventivefibrous structure, and may exert a useful function if desired.

Uses for the fibrous structure of this invention, includepharmaceutical, medical and biotech processing and filtration, bloodprocessing including of whole blood and blood components, food andbeverage processing and filtration, diagnostic medical and veterinaryuses, and air and liquid filtration and separation uses. Important tothese uses is the immobilization of the fine active particles, andaccessibility of the gas or liquid to the immobilized fine activeparticles.

The fibrous structure may be used as is or in various forms or devices.The fibrous structure may be used singly or in combination with otherfabrics, filter media, films, plastics and membranes.

In a beneficial dry forming process for making the fibrous structure ofFIG. 1, a carding machine cards crimped fiber and forms an opennon-woven web 20 on an endless moving belt. Surrogate particles 30 areapplied to web 20 from, for instance, a shaker. Web 20 is open to anappropriate degree and surrogate particles 30 are of appropriate sizeand weight to become entrapped in the interior of the web. Then, heat isadvantageously applied without pressure to the surrogateparticles/fibrous matrix structure to provide for adhesion of thesurrogate particles to the fibrous matrix and for fiber-fiber bonding.In this way, a fibrous matrix is formed, and thereafter surrogateparticles are distributed in a three dimensional arrangement and fixedto a stabilized fibrous matrix.

Other ways of fixing the surrogate particles may be used. A heat-bondingstep, if used, is carried out at a sufficient elevated temperature lessthan the melting point of the structural fiber component and for asuitable period of time to cause adhesion of the surrogate particles tothe structural fiber. The fibrous structure is then cooled.

Thereafter, in accordance with the invention, fine, mobile activeparticles are added to the stabilized surrogate particles/fibrous matrixstructure and based upon a preferential attraction between the fine,mobile particles and the fixed surrogate particles, the fine, mobileparticles are selectively deposited and immobilized on and in thesurrogate particles. A suitable deposition methodology is selectedconsistent with the considerations previously described; thus, thedeposition may be preceded by providing the surrogate particles and fineactive particles with attractive charges or forces. Accordingly by thisinvention, there is also provided a method by which a stabilized fibrousmatrix with fixed surrogate particles is prepared, and thereafter fine,mobile active particles are selectively deposited and immobilized on thefixed surrogate particles using suitable deposition conditions.

The present invention may be carried out with various modificationswithout departing from the spirit or essential attributes thereof, andaccordingly, reference should be made to the appended claims, ratherthan to the foregoing specification as indicating the scope of theinvention.

We claim:
 1. A fibrous structure comprising surrogate particles bearingfunctionally active, fine particles, wherein said surrogate particlesare entrapped in and bonded to a fibrous matrix in a three dimensionalarrangement, wherein the average size of said functionally active, fineparticles is on the order of approximately 0.01 to 0.0001 of the averagesize of said surrogate particles, wherein said functionally active, fineparticles are disposed on said surrogate particles in a significantlygreater amount than on said fibrous matrix, and are immobilized on saidsurrogate particles.
 2. The fibrous matrix of claim 1, wherein saidsurrogate particles comprise pores, and wherein a portion of saidfunctionally active, fine particles is disposed within said pores. 3.The fibrous structure of claim 2, wherein said fine particles are of anaverage size sufficiently smaller than the average size of said pores,for accessibility to said portion of immobilized fine particles by a gasor liquid.
 4. The fibrous structure of claim 1, wherein said fineparticles are in a monolayer.
 5. The fibrous structure of claim 1,wherein said average size of said functionally active, fine particles isin the range of from about 0.01 to 10 microns.
 6. The fibrous structureof claim 1, wherein the immobilization of said fine active particles isby attractive association with, or attachment to, said surrogateparticles.
 7. The fibrous structure of claim 1, wherein said surrogateparticles are selected from the group consisting of carbon particles,zeolite particles, alumina particles, polymeric particles and absorbentparticles.
 8. The fibrous structure of claim 1, wherein said threedimensional arrangement is a generally uniform, three dimensionallyspaced apart arrangement.
 9. The fibrous structure of claim 8,comprising tortuous flow paths.
 10. The fibrous structure of claim 1,wherein said fine particles have a function selected from at least oneof a processing function, analytical function and sorptive function. 11.The fibrous structure of claim 1, wherein said fibrous matrix comprisescomposite fiber comprising a heat-bondable fiber component, and whereinsaid surrogate particles are bonded to said fibrous matrix by saidheat-bondable component.
 12. The fibrous structure of claim 1, whereinsaid surrogate particles are high available surface, surrogate particlesand further comprising at least one layer disposed on or within saidfibrous structure.
 13. A fibrous structure comprising high availablesurface, surrogate particles bearing functionally active, fineparticles, wherein said surrogate particles are entrapped in and bondedto a fibrous matrix in a three dimensional arrangement, wherein theaverage size of said fine particles is on the order of approximately0.01 to 0.0001 of the average size of said surrogate particles, andwherein said functionally active, fine particles are immobilized on saidsurrogate particles.
 14. The fibrous structure of claim 13, wherein saidsurrogate particles comprise pores, and wherein a portion of theimmobilized fine particles is disposed within said pores.
 15. Thefibrous structure of claim 14, wherein said fine particles are of anaverage size sufficiently smaller than the average size of said pores,for accessibility to said portion of immobilized fine particles by a gasor liquid.
 16. The fibrous structure of claim 13, wherein said fineparticles are in a monolayer.
 17. The fibrous structure of claim 13,wherein the immobilization of said fine active particles is byattractive association with, or attachment to, said surrogate particles.18. The fibrous structure of claim 13, wherein said fine particles havea function selected from at least one of a processing function,analytical function and sorptive function.
 19. The fibrous structure ofclaim 13, wherein said fibrous matrix comprises composite fibercomprising a heat-bondable fiber component, and wherein the bonding tosaid fibrous matrix is by said heat-bondable component, furthercomprising at least one layer disposed on or within said fibrousstructure.